Gasket

ABSTRACT

A longitudinally-endless gasket mounted into a groove portion formed in one of members to provide sealing between the one member and the other member when they are fastened to each other. The gasket has a sectional shape corresponding to a sectional shape of the groove portion with a ratio (H/W) between the height (H) and the width (W) of the section being 0.8 to 5.0. The gasket is provided with a plurality of large projecting portions at intervals of 30 to 100 mm and a plurality of small projecting portions at intervals of 5 to 15 mm in a longitudinal direction of the gasket. The width (R2) of each the large projecting portion is larger than the width (X) of the groove portion by 0.01 to 0.9 mm. The width (R1) of each of the small projecting portion is smaller than the width (X) of the groove portion by 0.01 to 0.6 mm. A filling rate of the groove portion by the gasket when the one member and the other member are fastened to each other is 80 to 100%.

[0001] This application is a continuation of International ApplicationNo. PCT/JP02/07106, with an international filing date of Jul. 12, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a sealing arrangement betweenmembers in close contact with each other and to a longitudinally-endlessgasket mounted into a groove portion formed in one of the members toprovide sealing between the one member and the other member when theyare fastened to each other.

[0004] For example, the present invention relates to a sealingarrangement between an intake manifold and a cylinder head in an enginemounted to an automobile or the like. To put it more concretely, theinvention relates to a longitudinally-endless gasket mounted into agroove portion formed in a face of an intake manifold disposed to face acylinder head of the engine. The face of the intake manifold in whichthe groove portion is formed also faces the cylinder head of the engine.When the intake manifold and the cylinder head are fastened to eachother, the longitudinally-endless gasket mounted into the groove portionprovides sealing between them.

[0005] 2. Description of the Related Art

[0006] As a longitudinally-endless gasket mounted into a groove portionformed in one of members to provide sealing between the one member andthe other member when they are fastened to each other, there is a knowngasket for providing sealing between an intake manifold and a headmember of an engine mounted to an automobile or the like.

[0007] Conventionally, as a gasket for providing sealing between anintake manifold and a head member of an engine mounted to an automobileor the like, a rubber gasket made of an elastic body such as syntheticrubber and having a rectangular or oval sectional shape is used.

[0008] The rubber gasket for the intake manifold is inserted into agroove portion formed in a face of the intake manifold facing thecylinder head during a mounting operation process. At this time, manyportions of the rubber gasket are inserted into the groove portion and atip end side is exposed from the groove portion. A face of the tip endside exposed from the groove portion is brought into contact with thecylinder head in a succeeding tightening operation. When the intakemanifold and the cylinder head are fastened to each other in thetightening process, the rubber gasket is brought into close and tightcontact with the inner walls of the groove portion of the intakemanifold and the cylinder head through compressive elastic deformation,thereby required sealing operation can be obtained. Fastening of theintake manifold and the cylinder head to each other in the tighteningprocess is normally carried out by using fastenings such as boltsdisposed in a vicinity of the groove portion.

[0009] In such a prior-art rubber gasket, there were problems such asincomplete insertion of the gasket into the groove portion in theoperation process of mounting the gasket into the groove portion of theintake manifold and falling down of the rubber gasket during thetightening process.

[0010] In other words, to describe it by referring to the drawings, asshown in FIG. 11, a prior-art gasket for the intake manifold, e.g., arubber gasket 1 formed of an elastic body such as synthetic rubber orthe like is formed into a shape of a thin O-ring having an ovalsectional shape which is long in a vertical direction to meet a recentdemand for weight reduction. Such a rubber gasket 1 has a poor shapemaintaining property because of its thin shape. Therefore, it isdifficult to quickly and reliably insert the gasket in the operationprocess of mounting the gasket into the groove portion 21 of the intakemanifold 2. After inserting the rubber gasket 1 into the groove portion21, the tightening operation for fastening the intake manifold 2 and thecylinder head 3 in directions shown with arrows 101 and 102 is carriedout at tightening torque of about 4.9 MPa to 9.8 MPa by using fasteningssuch as bolts or the like disposed in a vicinity of the groove portion.During this tightening process, because the rubber gasket 1 is in theshape of an O-ring having an oval sectional shape which is long in thevertical direction, the gasket 1 is likely to be displaced outward fromthe groove portion 21 and to fall down in a diagonal direction to befastened.

[0011] In a normal assembly line of the engine of an automobile, afterthe rubber gasket 1 is mounted into the groove portion 21 of the intakemanifold 2, the mounting face of the intake manifold 2 is turned aroundinto a state shown in FIG. 11. Then, the operation for tightening theintake manifold 2 and the cylinder head 3 against each other is carriedout.

[0012] If means, such as elastic projecting portions 22 a, 22 b, and thelike, provided to opposite side faces of the rubber gasket 1 facing theopposite inner wall faces of the groove portion 21, for preventing therubber gasket 1 from falling off, is insufficient, the rubber gasket 1falls off from the groove portion 21 in the turning around, an insertedposition is displaced to cause poor sealing, or more serious damage iscaused in some cases.

[0013] If large means of preventing falling off is provided in order tocope with the above problems, it becomes difficult to insert the rubbergasket 1 into the groove portion 21.

[0014] Therefore, a gasket which has such an excellent workability thatthe mounting and tightening operations can be carried out easily andwhich can be reliably mounted is required.

[0015] Because the gasket for the intake manifold and formed into theshape of a thin O-ring having an oval sectional shape which is long inthe vertical direction to meet the recent demand for weight reduction islikely to fall down when it is subjected to strong tightening, acompression rate is set at a low value to cope with this problem.However, low tightening in which the compression rate is set at a lowvalue exerts a considerable bad influence on the sealing property.

[0016] The before described problems of the gasket for the intakemanifold of the engine mounted to the automobile or the like are commonto a longitudinally-endless gasket (e.g., a rocker cover gasket, a frontcover gasket, an oil pan gasket, a timing chain cover gasket, and thelike) mounted into a groove portion formed in one of members to providesealing between the one member and the other member when they arefastened to each other.

[0017] In view of the above-described problems of thelongitudinally-endless gasket for providing sealing between the onemember and the other member when they are fastened to each other, it isan object of the present invention to provide a gasket which has such anexcellent workability that mounting and tightening operations can becarried out easily and which can exert satisfactory sealing performance.

SUMMARY OF THE INVENTION

[0018] To solve the above problems, a gasket proposed by the inventionhas a sectional shape corresponding to a sectional shape of a grooveportion in which the gasket is fitted. A ratio (H/W) between the height(H) and the width (W) of the cross section is in a specific range. Thegasket is provided with a plurality of large projecting portions and aplurality of small projecting portions respectively at predeterminedintervals (P), (p) in a longitudinal direction, each of the projectingportions formed with projections projecting from opposite side faces.There are predetermined differences (ΔX), (Δx) between widths (R2), (R1)of the small and large projecting portions and a width (X) of the grooveportion. A filling rate of the groove portion by the gasket when onemember having the groove portion in which the gasket is fitted and theother member are fastened to each other is 80 to 100%.

[0019] The gasket of the present invention which is employed as a gasketfor an intake manifold of an engine mounted to an automobile or the likewill be described below in detail by referring to the accompanyingdrawings.

[0020] The gasket 4 of the invention is a longitudinally endless gasketmounted into a groove portion 21 formed in a face of an intake manifold2 disposed to face a cylinder head 3. The face of the intake manifold 2in which the groove portion 21 is formed also faces the cylinder head 3.When the intake manifold 2 and the cylinder head 3 are fastened to eachother, the gasket 4 mounted into the groove portion 21 provides sealingbetween them.

[0021] The gasket 4 of the invention has a sectional shape correspondingto a sectional shape of the groove portion 21.

[0022] The ratio (H/W) between the height (H) of a section of the gasket4 of the invention in a depth direction of the groove portion 21 formedin the intake manifold 2 and the width (W) of the section in a widthdirection of the groove portion 21 is 0.8 to 5.0.

[0023] As shown in FIG. 3, the gasket 4 of the invention includes in alongitudinal direction thereof a plurality of large projecting portions42 and the like formed with projections 42 a, 42 b, and the likeprojecting from opposite side faces facing the opposite inner wall facesof the groove portion 21, formed in the intake manifold 2, toward theopposite inner wall faces of the groove portion 21.

[0024] As shown in FIG. 3, the gasket 4 of the invention includes in alongitudinal direction thereof a plurality of small projecting portions41 and the like formed with projections 41 a, 41 b, and the likeprojecting from the opposite side faces facing the opposite inner wallfaces of the groove portion 21 formed in the intake manifold 2 towardthe opposite inner wall faces of the groove portion 21.

[0025] The large projecting portions 42 and the like adjacent to eachother in the longitudinal direction of the gasket 4 are disposed atintervals (P) of 30 to 100 mm. The dimension (R2) of each of the largeprojecting portions 42 and the like in the width direction of the grooveportion 21 is larger than a dimension (X) of the groove portion 21 inthe width direction by 0.01 mm to 0.9 mm. The dimension (R2) of thelarge projecting portion 42 in the width direction is shown in FIG. 2showing a section taken along a line B-B in FIG. 3.

[0026] The small projecting portions 41 and the like are disposed withintervals (p) of 5 to 15 mm between the small projecting portionsadjacent to each other and between the large projecting portion adjacentto each other in the longitudinal direction of the gasket 4. Thedimension (R1) of each of the small projecting portions 41 and the likein the width direction of the groove portion 21 is smaller than thedimension (X) of the groove portion 21 in the width direction by 0.01 mmto 0.6 mm. The dimension (R1) of each of the small projecting portions41 and the like in the width direction is shown in FIG. 1 showing asection taken along a line A-A in FIG. 3.

[0027] In addition to the above constitution/structures, a filling rateof the groove portion 21 by the gasket 4 of the invention when theintake manifold 2 and the cylinder head 3 are fastened to each other is80 to 100%.

[0028] The gasket of the invention is in an annular shape which isendless in a longitudinal direction. A portion of the annular gasket 4is shown in FIGS. 3 and 4 which show a state in which the gasket 4 ismounted in the groove portion 21 of the intake manifold 2 viewed from aside of the cylinder head 3.

[0029] The gasket of the invention can be formed by using lightweightmaterial which can meet the demand for weight reduction of an engine andthe like of an automobile. As such light weight material, syntheticresin material and lightweight metal material which are known in the artcan be used.

[0030] As the synthetic resin material, there is synthetic rubbermaterial, for example. The gasket of the invention and produced by aknown method by using the synthetic rubber material becomes a rubbergasket.

[0031] As synthetic rubber material, butyl rubber,styrene-butadienecopolymer, ethylene-vinyl acetate copolymer,ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer,butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, acrylicrubber, silicon rubber, fluorine rubber, fluorosilicon rubber, ethylenepropylene rubber, and the like can be employed.

[0032] As lightweight metal material, aluminum, magnesium, and the likecan be employed.

[0033] The gasket of the invention can be produced by using theabove-described synthetic rubber material and lightweight metal materialand by using the producing method employed conventionally in the art.

[0034] Because the gasket of the invention includes the above-describedlarge projecting portions 42 and the like having the characteristicstructures, it is possible to reduce risks of poor sealing caused byfalling off the gasket from the groove portion 21 or displacement of aninserted position of the gasket during a mounting operation process anda tightening process. Therefore, the mounting operation and thetightening operation can be carried out easily.

[0035] Because the gasket includes the above-described small projectingportions 41 and the like having the characteristic structures, it ispossible to effectively prevent generation of a lateral drift or fallingdown of the gasket during the tightening process.

[0036] Because of the above-described cross sectional shape, thespecific ratio (H/W) between the height (H) and the width (W) of thesection shown in FIGS. 1 and 2, and the above-described filling rate inaddition to the constitution/structure having the small projectingportions and the large projecting portions, the gasket can exert itsexcellent sealing performance.

[0037] The before described sectional shape of the gasket of the presentinvention corresponding to the sectional shape of the groove portionrefers to such a correspondence that an outer wall face (opposite sidefaces and an upper face in FIGS. 1 and 2) of the gasket 4 are disposedalong the inner wall faces of the groove portion 21 and fits well in thegroove portion 21 as shown in FIGS. 1 and 2 when the gasket 4 isinserted into the groove portion 21 in the mounting operation process.This means that the sectional shape of the gasket 4 is in asubstantially rectangular shape as shown in FIGS. 1 and 2 to correspondto the sectional shape of the groove portion 21 when the sectional shapeof the groove portion 21 formed in the face of the intake manifold 2facing the cylinder head 3 is in a substantially rectangular shape, forexample, as shown in FIGS. 1 and 2. As a result, the inner wall faces ofthe groove portion 21 and the outer wall faces of the gasket 4 are inuniform contact with each other to allow the gasket 4 to fully exert itselasticity when the intake manifold 2 and the cylinder head 3 arefastened to each other.

[0038] The ratio (H/W) between the height (H) and the width (W) of thecross section is 0.8 to 5.0 as described above because it is preferablethat the ratio is in this range for the reason that respective faces(upper and lower faces and opposite side faces in FIGS. 1 and 2) of thegasket 4 can respectively be in uniform contact with a bottom face andopposite inner wall faces of the groove portion 21 and the cylinder head3 when the intake manifold 2 and the cylinder head 3 are fastened toeach other and the gasket 4 can exert its elasticity to obtain a highsealing force.

[0039] The dimension of the large projecting portion is as describedabove, i.e., ΔX/2+ΔX/2=ΔX=0.01 to 0.9 mm in FIGS. 2 to 4 because thisdimension is preferable in order to smoothly insert the gasket 4 intothe groove portion 21 and to reduce the risks of poor sealing caused byfalling off of the gasket 4 from the groove portion 21 or displacementof the inserted position of the gasket during the mounting operationprocess and the tightening process.

[0040] Here, the dimension of the large projecting portion is preferablyΔX/2+ΔX/2=ΔX=0.1 to 0.3 mm in FIGS. 2 to 4 in order to exert the beforedescribed effects.

[0041] The above-described interval (P) at which the large projectingportions are provided in the longitudinal direction of the gasket, theinterval (p) at which the small projecting portions are provided in thelongitudinal direction of the gasket, and the above-described dimensionof the small projecting portion, i.e., Δx/2+Δx/2=Δx=0.01 to 0.6 mm inFIGS. 1, 3, and 4 are desirable for the following reasons. With theabove intervals and dimension, it is possible to effectively preventlateral drift and falling down of the gasket during the tighteningoperation while corresponding to the above-described dimension of thelarge projecting portion. Moreover, the above intervals and dimensionare desirable because the respective faces (upper and lower faces andopposite side faces in FIGS. 1 and 2) of the gasket 4 can respectivelybe in uniform contact with the bottom face and opposite inner wall facesof the groove portion 21 and the cylinder head 3 and the gasket 4 canexert its elasticity to obtain the high sealing force with suchintervals and dimension together with the above-described crosssectional shape, the above-described specific ratio (H/W) between theheight (H) and the width (W), and the above-described filling rate whenthe intake manifold 2 and the cylinder head 3 are fastened to eachother.

[0042] The dimension of the small projecting portion is preferably in arange of Δx/2+Δx/2=Δx=0.1 to 0.3 mm in order to exert the beforedescribed effects better.

[0043] As dimensions of the above large projecting portions 42 and thelike and small projecting portions 41 and the like, the followingexamples can be given, where the width of the groove portion 21 is (X),the width of the section of the gasket at a position at which the smallprojecting portion 41 or the like is provided and in the width directionof the groove portion 21 is (R1), and the width of the section of thegasket at a position at which the large projecting portion 42 or thelike is provided and in the width direction of the groove portion 21 is(R2). X (mm) R1 (mm) R2 (mm) 2 1.9 2.1 2 1.7 2.3 3 2.9 3.1 3 2.7 3.3 43.9 4.1 4 3.7 4.3 5 4.9 5.1 5 4.7 5.3 7 6.9 7.1 7 6.7 7.3 10 9.9 10.1 109.7 10.3

[0044] Although the width (X) of the groove portion 21 is not limited tothe above examples, with respect to various widths (X) of the grooveportion 21, the gasket of the present invention can be provided bysetting the large projecting portions and small projecting portions ofdimensions having a relationship shown in the above examples, thesectional shape corresponds to the sectional shape of the groove portion21, the ratio (H/W) between the height (H) and the width (W) of thesection is 0.8 to 5.0, the intervals (P), (p) at which the largeprojecting portions and small projecting portions are provided in theabove-described ranges, and the filling rate of the groove portion 21 bythe gasket when the intake manifold and the cylinder head are fastenedto each other is 80 to 100%.

[0045] In the gasket of the invention, the filling rate of the grooveportion 21 by the gasket when the intake manifold 2 and the cylinderhead 3 are fastened to each other is 80 to 100% as described above,because the filling rate in such a range in addition to theabove-described constitution and structure including the smallprojecting portions and large projecting portions, the above-describedcross sectional shape, and the specific ratio (H/W) between the height(H) and the width (W) is desirable in order to increase the compressionrate when the intake manifold 2 and the cylinder head 3 are fastened toeach other and to obtain a satisfactory sealing property.

[0046] In this specification, “the filling rate” refers to a percentageof volume of the gasket 4 in volume of the groove portion 21 when theintake manifold 2 and the cylinder head 3 are fastened to each other.

[0047] According to an experiment carried out by the inventors of thepresent application, the filling rate of 85% is the most desirable inorder to enhance the compression rate and to obtain the satisfactorysealing property in the gasket of the invention.

[0048]FIG. 6 shows a result of an experiment on a relationship betweenthe compression rate and the likelihood of occurrence of falling downwhen the gasket (rubber gasket) of the invention is formed by usingbutyl rubber as main material and the interval represented by areference character (p) in FIG. 3, i.e., the interval between the smallprojecting portions adjacent to each other and the interval between thesmall projecting portion and the large projecting portion adjacent toeach other in the longitudinal direction of the gasket are changed. Inthe rubber gasket subjected to the experiment, the lateral width (W)=1.6mm, the relationship between the height and the width: H/W=3.6, thedimension of the small projecting portion: R1=2.8 mm, and the dimensionof the large projecting portion: R2=3.2 mm. The rubber gasket of theinvention was inserted into the groove portion of the width (X)=3.0 mmand depth: 4 mm and the intake manifold having the groove portion and ahead member are fastened to each other to carry out the experiment. InFIG. 6, ∘ represents a result of the experiment under the condition ofp=5 mm, Δ represents that under the condition of p=15 mm, and Xrepresents that under the condition of p=20 mm. A horizontal axisrepresents the compression rate (%) (the compression rate increasesrightward) and a vertical axis represents a likelihood of occurrence offalling down (the likelihood of occurrence of falling down increasesdownward). From this experiment result, if (p) is larger than 15 mm, thelikelihood of occurrence of falling down increases if the compressionrate is increased so as to obtain better sealing property. Therefore, itis preferable that (p) does not exceed 15 mm. In consideration of easeof production and the like, it is preferable that (p) is not smallerthan 5 mm.

[0049] In the gasket of the invention, the interval (P) between thelarge projecting portions adjacent to each other in the longitudinaldirection of the gasket is preferably in a range of 30 to 100 mm and theinterval (p) between the small projecting portions adjacent to eachother and the interval (p) between the small projecting portion and thelarge projecting portion adjacent to each other in the longitudinaldirection of the gasket are preferably in the range of 5 to 15 mm. It ispossible to employ a form shown in FIG. 3 in which one small projectingportions 41 and 51 are disposed respectively between the adjacent largeprojecting portion 42 and large projecting portion 52 and between thelarge projecting portion 52 and large projecting portion 62 or it isalso possible to employ a form shown in FIG. 4 in which a plurality ofsmall projecting portions 61, 71, 81, 91, 101, and 111 are respectivelydisposed between the adjacent large projecting portion 72 and largeprojecting portion 82, between the large projecting portion 82 and largeprojecting portion 92, and between the large projecting portion 92 andlarge projecting portion 102.

[0050] There is no difference in exerted operation and effects betweenthe form shown in FIG. 3 and the form shown in FIG. 4 as long as thegasket has a shape and a structural characteristic required of thegasket of the invention. However, it is preferable that at least onesmall projecting portion is disposed between the large projectingportions adjacent to each other to make sure that falling down of thegasket due to compressive lateral drift deformation in tightening isprevented.

[0051] As shown in FIGS. 3 and 4, in the small projecting portions 41,51, 61, and the like, projections 41 a, 41 b, 51 a, 51 b, 61 a, and 61 bprojecting from the opposite side walls of the gasket toward the innerwall faces of the groove portion 21 facing the side walls are preferablyprovided symmetrically with respect to a center line (C1) of the gasket4. In the large projecting portions 42, 52, 62, 72, and the like,projections 42 a, 42 b, 52 a, 52 b, 62 a, 62 b, 72 a, and 72 bprojecting from the opposite side walls of the gasket toward the innerwall faces of the groove portion 21 facing the opposite side walls arepreferably provided symmetrically with respect to the center line (C1)of the gasket 4. A purpose for this is to exert effects of facilitatingthe inserting process and preventing falling down better.

[0052] In addition to this, it is further advantageous that thedimension of the small projecting portion and the dimension of the largeprojecting portion defining dimensions represented by Δx, ΔX in FIGS. 1to 4 are set at such a condition of Δx=ΔX in one gasket (i.e., in thesame gasket) from a viewpoint of ease of the inserting operation and aneffect of preventing falling down. Each of the embodiments shown inFIGS. 1 to 4 shows a case of Δx=ΔX.

[0053] In the invention, the above-described intervals (P), (p) aremeasured at positions of the center line (C1) of the gasket.

[0054] The above-described gasket of the invention may be formed into astructure in which an upper face and/or a lower face corresponding to adepth direction of the groove portion 21 of the intake manifold 2 are(is) respectively formed with ribs. FIGS. 1 and 2 show forms in whichthe upper face and lower face of the gasket 4 are respectively formedwith ribs 43, 43.

[0055] In this case, a structure in which the upper face and/or lowerface of the gasket are (is) formed with a plurality of ribs at differentpositions in the width direction of the groove portion 21 of the intakemanifold 2 is also possible. FIGS. 7 and 8 show forms in which the upperface and lower faces of the gasket 4 are respectively formed with aplurality of ribs 143, 143, 243, 243, and 243 according to requiredfunctions.

[0056] It is advantageous to provide such ribs because the sealingperformance can be enhanced. Provision of such ribs is advantageousbecause the upper and lower faces of the gasket which respectively abuton the bottom face of the groove portion 21 and the abutting face of thecylinder head 3 can be easily and elastically deformed in the widthdirection (i.e., a lateral direction in FIGS. 1 and 2) when the intakemanifold 2 and the cylinder head 3 are fastened to each other.

[0057] Furthermore, in the above-described gasket of the invention, ifthe sectional shape of the gasket is substantially rectangular, cornerportions of the rectangular shape may be formed to have acute angles.For example, if the sectional shape of the groove portion 21 issubstantially rectangular as shown in FIGS. 1 and 2, the sectional shapeof the gasket is also substantially rectangular as shown in FIGS. 1 and2 to correspond to the shape of the groove portion 21. In this case,corner portions 44 are formed to have acute angles as shown in FIGS. 9and 10.

[0058] Such acute-angled corner portions 44 function as edges whichlocally come in contact with the corner portions of the bottom face ofthe groove portion 21 in the intake manifold 2 when the intake manifold2 and the cylinder head 3 are fastened to each other. Surface pressureat each of the corner portion of the bottom face of the groove portion21 is increased by local surface pressure generated in the local contactportion to ensure better sealing performance. In other words, theacute-angled edge formed at the corner portion 44 comes in local contactwith the interior angle portion of the groove portion 21 by tighteningof the intake manifold 2 and the cylinder head 3 to each other. Thus,local surface pressure is generated in this portion and the surfacepressure of the corner portion is increased. In FIG. 10, although thecorner portions are chamfered, the corner portions 44 are formed intoacute-angled edges.

[0059] The gasket of the invention includes, as shown in FIGS. 1 to 4,the plurality of large projecting portions 42 and the like formed withprojections projecting from the opposite side faces facing the oppositeinner wall faces of the groove portion 21 formed in the intake manifold2 toward the opposite inner wall faces of the groove portion 21 and theplurality of small projecting portions 41 and the like respectively atpredetermined intervals (P), (p) in the longitudinal direction of thegasket. The dimensions (R2), (R1) of the large projecting portions 42and the like and the small projecting portions 41 and the like in thewidth direction of the groove portion 21 are maintained at predetermineddimensions with respect to the dimension (X) of the groove portion 21 inthe width direction. Thus, falling off of the gasket in mounting andfalling down of the gasket due to the compressive lateral driftdeformation in tightening are prevented thoroughly.

[0060] In other words, the dimension (R2) of the large projectingportions 42 and the like in the width direction of the groove portion 21is larger than the width (X) of the groove portion 21 by ΔX=0.01 mm to0.9 mm while the dimension (R1) of the small projecting portions 41 andthe like in the width direction of the groove portion 21 is smaller thanthe width (X) of the groove portion 21 by Δx=0.01 mm to 0.6 mm. Thelarge projecting portions 42 and the like are provided at intervals of30 to 100 mm and the small projecting portions 41 and the like areprovided at intervals of 5 to 15 mm. Moreover, the sectional shape ofthe gasket 4 corresponds to the sectional shape of the groove portion21. In order to insert the gasket 4 into the groove portion 21, portionsprovided with the large projecting portions 42 and the like are pushedinto the groove portion 21 and are inserted while being pressed againstthe opposite inner walls of the groove portion 21. Then, the otherportions including portions provided with the small projecting portions41 and the like can be extremely easily fitted in the groove portion 21while being pulled by the portions provided with the large projectingportions 42 and the like. Then, the gasket fits as shown in FIGS. 1 and2.

[0061] The portions provided with the small projecting portions 41 andthe like are mounted along the wall face of the groove portion 21.Therefore, if the intake manifold 2 and the cylinder head 3 are fastenedin directions shown with arrows 101 and 102 by fastenings such as boltsor the like (not shown) from the state shown in FIGS. 1 and 2, thegasket 4 is compressed, sandwiched between the groove portion 21 and thecylinder head 3, and elastically deformed to come in contact with theinner faces of the groove portion 21 and the contact face of thecylinder head 3 through a large area of the gasket 4.

[0062] At this time, a gap (Δx) between each of the projections 41 a, 41b, and the like of the small projecting portions 41 and the like and theopposite inner wall faces of the groove portion 21 is gradually narroweddue to deformation of the main body of the gasket 4 and the projections41 a, 41 b, and the like come in contact with the inner wall faces ofthe groove portion 21. Thus, the lateral drift and falling down of thegasket between the large projecting portions 42 and the like can beeffectively prevented.

[0063] On the other hand, because the projections 41 a, 41 b, 42 a, 42b, and the like of the small projecting portion 41 and the like and thelarge projecting portion 42 and the like are projecting from the mainbody of the gasket in directions of the side faces, they are notseriously affected by the elastic deformation of the main body portionof the gasket 4 and are mounted into the groove portion 21 from theshapes when they are inserted into the groove portion 21 for the firsttime as a starting point. Then, together with the characteristicstructures such as the sectional shape corresponding to the sectionalshape of the groove portion 21, the specific ratio (H/W) between theheight (H) and the width (W) of the section, and the specific fillingrate, satisfactory sealing property can be exerted.

[0064] As described above, in the gasket of the invention, because theplurality of large projecting portions and the plurality of smallprojecting portions having different dimensions (R2), (R1) in the widthdirection of the groove portion in which the gasket is fitted areprovided at different intervals (P), (p) in the longitudinal directionof the gasket and also because the sectional shape of the gasket and thefilling rate are taken into consideration, amounting property isimproved, the function of preventing falling off can be improved, andfalling down in tightening can be prevented. Furthermore, by the fillingrate in the above-described range, it is possible to set the compressionrate at a high value, which greatly contributes to improvement of thesealing property.

[0065] The case of the gasket of the invention employed as the gasketfor the intake manifold of the engine mounted to the automobile or thelike has been described above.

[0066] Descriptions in the before described embodiments hold true forthe case of the gasket of the invention employed as alongitudinally-endless gasket (e.g., a rocker cover gasket, a frontcover gasket, an oil pan gasket, and a timing chain cover gasket)mounted into a groove portion formed in one of members to providesealing between the one member and the other member when they arefastened to each other.

[0067] Although the invention has been described above in detail byreference to the accompanying drawings, structures and dispositionrelationships are only roughly shown in the drawings to such an extentas to allow understanding of the invention. Dimensions, materials, andthe like of the respective components in the accompanying drawings anddescription in the present specification are only examples. Therefore,the invention is not limited to the embodiments described here and inthe accompanying drawings and can be changed into various forms withoutdeparting from a technical scope grasped from description of claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0068]FIG. 1 is a sectional view of an example of mounting of a gasketof the present invention;

[0069]FIG. 2 is a sectional view of the example of mounting of thegasket of FIG. 1 taken at another position;

[0070]FIG. 3 is a plan view of the gasket shown in FIG. 1 and mounted ina groove portion of an intake manifold with the gasket viewed from aside of a cylinder head and with a portion omitted;

[0071]FIG. 4 is a plan view of another gasket of the invention andmounted in the groove portion of the intake manifold with the gasketviewed from the side of the cylinder head and with a portion omitted;

[0072]FIG. 5(a) is a plan view of an example of the gasket of theinvention;

[0073]FIG. 5(b) is a sectional view taken along a line C-C in FIG. 5(a);

[0074]FIG. 5(c) is a sectional view taken along a line D-D in FIG. 5(a);

[0075]FIG. 5(d) is a sectional view taken along a line E-E in FIG. 5(a);

[0076]FIG. 6 shows a result of an experiment on a relationship betweenthe compression rate and occurrence of falling down when intervals atwhich small projections provided to the gasket of the invention aredisposed are changed;

[0077]FIG. 7 is a sectional view showing another embodiment of theinvention at a position corresponding to a section taken along a lineA-A in FIG. 3;

[0078]FIG. 8 is a sectional view showing still another embodiment of theinvention at a position corresponding to a section taken along a lineB-B in FIG. 3;

[0079]FIG. 9 is a sectional view showing still another embodiment of theinvention at a position corresponding to a section taken along a lineA-A in FIG. 3;

[0080]FIG. 10 is a sectional view showing still another embodiment ofthe invention at a position corresponding to a section taken along aline B-B in FIG. 3; and

[0081]FIG. 11 is a sectional view of an example of mounting of aprior-art gasket for an intake manifold.

DETAILED DESCRIPTION OF THE INVENTION

[0082] A rubber gasket 104 of the present invention shown in FIG. 5(a)is formed by using acrylic rubber as synthetic rubber material, addingand mixing a rubber chemical agent into the acrylic rubber to haveunvulcanized rubber ready, vulcanizing and molding the unvulcanizedrubber into an annular shape by using a mold.

[0083] The rubber gasket 104 includes in its longitudinal directionlarge projecting portions 132, 142, 152, and 162 and small projectingportions 121, 131, 141, 151, 161, 171, 181, and 191. In each of thelarge projecting portions 132 and the like, projections 162 a and 162 bare formed symmetrically on opposite side walls of the rubber gasket 104as shown in FIG. 5(d). In each of the small projecting portions 121 andthe like, the projections 121 a and 121 b are formed symmetrically onopposite side walls of the rubber gasket 104 as shown in FIG. 5(c).

[0084] In FIG. 5(b) showing a section taken along a line C-C in FIG.5(a), the condition is (w)=1.6 mm and (H)=5.7 mm. In FIG. 5(c) showing asection taken along a line D-D, the condition is (R1)=2.8 mm. In FIG.5(d) showing a section taken along a line E-E, the condition is (R2)=3.2mm.

[0085] The interval between the large projecting portions adjacent toeach other in the longitudinal direction of the rubber gasket 104, e.g.,the interval between the large projecting portions 132 and 142 is 34.5mm.

[0086] The interval between the large projecting portion 132 and thesmall projecting portion 121 adjacent to each other in the longitudinaldirection of the rubber gasket 104, the interval between the smallprojecting portion 121 and the small projecting portion 131, and theinterval between the small projecting portion 131 and the largeprojecting portion 142 are 11.5 mm.

[0087] The rubber gasket 104 was inserted into the groove portion (witha depth: 4.0 mm, a groove width (X)=3.0 mm, and a substantiallyrectangular sectional shape) of the intake manifold.

[0088] The portions of the rubber gasket 104 provided with the largeprojecting portions 132 to 162 were pushed into the groove portion andwere inserted into the groove portion while being pressed againstopposite inner walls. As a result, the other portions including portionsprovided with the small projecting portions 121 to 191 were pulled bythe portions provided with the large projecting portions and could beextremely easily fitted into the groove portion.

[0089] Then, the intake manifold was turned around into the state shownin FIG. 1 to face the cylinder head. The intake manifold and thecylinder head were tightened against each other and were fastened toeach other to produce a state in which sealing is provided between them.

[0090] During the operation process, there was no fear of falling off ofthe rubber gasket 104 from the groove portion and displacement of theinserted position of the rubber gasket 104.

[0091] The compression rate in tightening was 28% which was acompression rate high enough to ensure a satisfactory sealing property.A filling rate at this time was 85%.

[0092] The gasket of the invention is the longitudinally-endless gasketmounted into the groove portion formed in one of the members to providesealing between the one member and the other member when they arefastened to each other. For example, a gasket of the invention mountedinto a groove portion formed in a face of an intake manifold disposed toface a cylinder head of an engine mounted to an automobile. The face ofthe intake manifold in which the groove portion is formed also faces thecylinder head. When the intake manifold and the cylinder head arefastened to each other, the gasket provides sealing between them. Thegasket is also used as the rocker cover gasket, the front cover gasket,the oil pan gasket, or the timing chain cover gasket.

[0093] The gasket of the invention is a gasket which has such excellentworkability that mounting and tightening operations can be carried outeasily and which can exert satisfactory sealing performance. Therefore,the gasket can be used for a sealing arrangement between the intakemanifold and the cylinder head of the engine mounted to the automobileand the sealing arrangement in a rocker cover, a front cover, an oilpan, a timing chain cover, and the like.

What is claimed is:
 1. A longitudinally-endless gasket mounted into agroove portion formed in one of members to provide sealing between theone member and the other member when they are fastened to each other,wherein the gasket has a sectional shape corresponding to a sectionalshape of the groove portion with a ratio (H/W) between the height (H) ofthe section in a depth direction of the groove and the width (W) of thesection in a width direction of the groove portion being 0.8 to 5.0, thegasket is provided in a longitudinal direction thereof with a pluralityof large projecting portions and a plurality of small projectingportions each formed with projections projecting from opposite sidefaces facing opposite inner wall faces of the groove portion toward theopposite inner wall faces of the groove portion, the large projectingportions adjacent to each other in the longitudinal direction of thegasket are disposed at intervals of 30 to 100 mm, the width (R2) of eachof the large projecting portion in the width direction of the grooveportion being larger than the dimension (X) of the groove portion in thewidth-direction by 0.01 mm to 0.9 mm, the small projecting portionsadjacent to each other and the small projecting portion and the largeprojecting portion adjacent to each other in the longitudinal directionof the gasket are respectively disposed at intervals of 5 to 15 mm, thewidth (R1) of each of the small projecting portions in the widthdirection of the groove portion being smaller than the dimension (X) ofthe groove portion in the width direction by 0.01 mm to 0.6 mm, and afilling rate of the groove portion by the gasket when the one member andthe other member are fastened to each other that is 80 to 100%.
 2. Agasket according to claim 1, wherein an upper face and/or a lower faceof the gasket corresponding to the depth direction of the groove portionis/are provided with (a) rib(s).
 3. A gasket according to claim 2,wherein a plurality of ribs are formed in different positions in thewidth direction of the groove portion on the upper face and/or the lowerface of the gasket.
 4. A gasket according to claim 1, wherein thesectional shape of the gasket is substantially a rectangle and cornerportions of the rectangle are formed to have acute angles.
 5. A gasketaccording to claim 2, wherein the sectional shape of the gasket issubstantially a rectangle and corner portions of the rectangle areformed to have acute angles.
 6. A gasket according to claim 3, whereinthe sectional shape of the gasket is substantially a rectangle andcorner portions of the rectangle are formed to have acute angles.